1. Field of the Invention
The present invention relates to a stent. More particularly, it relates a sandwich stent which provides a mechanical barrier for prohibiting the growth of tissue through an artery implanted stent.
2. Description of the Prior art
In the prior art, stents are well known for use in minimally invasive surgery or interventional procedures for attaching to the inner walls of a blood vessel where a procedure such as a balloon angioplasty has been performed. Such prior art stents are essentially metallic scaffolds that are left in the arteries to prevent the arteries from collapsing back to their original form due to a phenomenon called elastic recoil. Such recoil can be common after the dilatation of a balloon.
Although the subject prior art stents have been generally successful in preventing elastic recoil, they have not been successful in the prevention of instent restenosis. Such phenomenon occurs when tissue grows into and through the struts of the stent due to openings in the stent struts. The tissue is then permitted to grow into the lumen and reocclude the artery, whereby a balloon angioplasty procedure most be repeated.
In an effort to prohibit instent restenosis, stents were provided with covering material. Such can be seen in U.S. Pat. No. 5,562,728 to Lazarus et al. wherein a helical wrap of ribbon is attached to a covering material; the attachment being only at the ends. U.S. Pat. No. 5,578,071 to Parodi et al. show a vascular graft that has two stents attached at the ends of the tubular conduit, where at one wire is provided and woven into a distal end, or lower end, of the graft, the wire permitting the distal end of the graft to conform to and sealingly engage within the artery of the patient.
When conveying a stent to its point of use, it is imperative that any covering material be secured about the stent in a secure and tight fashion to preclude the stent from being "hung up" in some area of the vascular system of the patient while it is being conveyed to the point of use. The prior art stents do not adequately secure the cover to the stent to prohibit such hang up. Further, the prior art devices have a very large profile that require being cut down by a surgeon and inserted into the body through a very large opening. Accordingly, minimally invasive surgery, in its strictest meaning, is not provided. Because of the large profile, the prior art devices are not useable in every area of the body, but only in larger arteries.
A stent is needed that overcomes the problems in the prior art. Such a stent needs to be low in profile yet provide the necessary mechanical barrier to prevent instent restenosis. An improved means of securement is needed to prevent the covering material hang up. Further, providing such an improved stent with a low profile can be used in widespread applications and not be limited to large artery procedures.